Pharmacotherapy is the cornerstone of Postherpetic Neuralgia (PHN) management. First-line treatments for PHN include antiviral agents (e.g., acyclovir, valacyclovir, famciclovir, and brivudine), centrally acting antiepileptic drugs (pregabalin and gabapentin), antidepressants (duloxetine and venlafaxine), and peripherally acting sodium-channel blockers (lidocaine patches).

In recent years, substantial progress has been made in the prevention and treatment of PHN, including early and active antiviral therapy (acyclovir, valacyclovir, famciclovir, brivudine, etc.), analgesic therapy (calcium-channel modulators such as pregabalin and gabapentin; tricyclic antidepressants such as amitriptyline; and opioid analgesics), interventional procedures (e.g., radiofrequency modulation and spinal cord stimulation), and vaccination. Nevertheless, clinical outcomes remain unsatisfactory, with the incidence of refractory PHN still exceeding 50%. Adverse effects associated with certain first- and second-line medications (such as antidepressants and anticonvulsants), as well as the potential risk of opioid dependence, markedly reduce treatment adherence. This situation has compelled clinicians to continually seek new and effective therapeutic approaches for PHN.

Non-invasive transcranial stimulation, as an emerging noninvasive neuromodulation technique, enables targeted modulation of deep brain structures. Animal studies have demonstrated that it can noninvasively regulate neuronal firing in deep regions and induce long-term plasticity, while offering relatively high spatial selectivity and tissue penetration. These features suggest broad clinical potential in chronic pain and affective disorders.

Inclusion Criteria:

• Age ≥ 18 years.
• Diagnosis of postherpetic neuralgia (PHN) with disease duration ≥ 3 months.
• NRS pain score ≥ 4.
• Willing to receive the intervention and able to provide written informed consent.

Exclusion Criteria:

• Contraindications to electrical stimulation (e.g., intracranial metal implants, cardiac pacemaker).
• History of epilepsy, severe psychiatric disorder, or cognitive impairment.
• Pregnant or breastfeeding women.
• Unable to comply with the intervention procedures and follow-up assessments.